The goal of the proposed research is to increase understanding of olfactory processing and the role played in olfactory plasticity by the olfactory cortex association fiber system. High-frequency stimulation of olfactory cortex association fibers has previously been shown to induce a novel form of potentiation in evoked field potentials. The proposed research will investigate the events underlying this potentiation using intracellular recordings from neurons in the olfactory cortex of intact animals, which permits the study of intracellular effects while preserving the network properties of the cortex. Preliminary data indicate that the primary intracellular effect produced by high-frequency association fiber stimulation, repeated daily for 4 to 6 days, is a pronounced hyperpolarization of the membrane potential of olfactory cortex pyramidal cells. The proposed research will further characterize this intracellular response and explore its functional significance. Specific aims of the proposed research are to: 1) compare the intracellular effects of high-frequency association fiber stimulation in naive vs. previously potentiated animals to determine whether prior potentiation is necessary to produce this effect; 2) determine whether the intracellular hyperpolarization is accomplished by enhanced inhibition or reduced synaptic drive (disfaciliation); and 3) examine the effect of the potentiation on the response of olfactory cortex pyramidal cells to stimulation of the afferent pathway to the cortex (lateral olfactory tract), tested with both electrical stimulation and naturally occurring odors. This research will provide an important contribution to the understanding of olfactory processing, thus aiding in the understanding and eventual treatment of olfactory disorders.